https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88766
--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot
com> ---
On Wed, 9 Jan 2019, msebor at gcc dot gnu.org wrote:
> I don't disagree with the conclusion about the validity of this test case but
> there are examples where GCC does treat a statement expression as an lvalue,
> such as in the following:
>
> void f (void)
> {
> int i = 0;
> ++__extension__({ (int)i; }); // accepted
> if (i != 1) // folded to false
> __builtin_abort ();
> }
>
> Accepting this seems like a bug irrespective of whether statement expressions
> themselves are ever lvalues.
Indeed. Casts as lvalues were removed a very long time ago.
> GCC of course also accepts ++({ i; }). Joseph's comment #2 suggests this
> should be invalid as well but I might be reading too much into it. In any
> case, it would be helpful to make this clear in the manual.
I think ++({ i; }) should be invalid. (If i is an _Atomic int, it's
already rejected because of the special lvalue-to-rvalue processing
applied for atomics.)
